Thyroid stimulating hormone (TSH) is one of a family of glycoprotein hormones that consist of two non-covalently linked, dissimilar subunits, designated alpha and beta. We are investigating the cellular events that take place in the biosynthesis of TSH; specifically, we wish to understand gene structure, organization, and regulation, the cellular mechanisms of post-translational processing of the alpha and beta subunits including cleavages of precursors, glycosylation, and assembly of chains. We wish to determine how these processes are regulated, how they may be interdependent, and how they may be involved in intracellular transport, packaging, and secretion of the hormone. An essential first approach to these studies is to obtain information about the primary structure of the subunits and their precursors. To accomplish this, we are using a transplantable thyrotroph tumor developed in our laboratory, and determining the primary sequences of the subunit precursors found by translations of thyrotroph tumor mRNA in heterologous cell-free systems. We are sequencing cDNAs made complementary to the subunit mRNAs. The sequencing of the cDNAs will provide information about the structure of both the coding and non-coding regions of the mRNAs for the subunits. This information of the primary structures will then be used in analyses of the structures of the alpha genes and the processes of glycosylation and post-translational cleavages of the subunit precursors. These initial studies will then provide the basis for subsequent studies of the cellular mechanisms involved in the regulation of subunit, assembly, and secretion mediated by thyrotrophin releasing hormone and thyroid hormones.